やばい

• やべえ (yabē)
• ヤベー (yabē)

Originally a slang term used in the criminal underworld,[1][2][3] used to indicate that the police were getting close.[1]

Derived as a shift to an -i adjective of older -na adjective やば (yaba, “illegal, dangerous, uneasy, not going well”), itself a slang term of uncertain derivation that appears in sources from the early 1800s.[1][2][3]

Possibly related to the ayabu- stem in 危ぶむ (ayabumu, “to fear something, to view something as dangerous”), and the ayau- stem in 危うい (ayaui, “dangerous”, ancient reading ayapui).

• (Tokyo) やば​い [yàbáꜜì] (Nakadaka – [2])[2][4]
• IPA^(key): [ja̠ba̠i]

やばい (-i inflection, hiragana and katakana ヤバい, rōmaji yabai)

1. (colloquial) dangerous, risky, bad

   ちゃんとしなきゃやべぇことになるぞ

   chanto shinakya yabē koto ni naru zo

   if you don't do it like you should, shit's gonna be bad, man

   (literally, “if you don't do it properly, it will become bad things”)

2. (colloquial) risque, off-color, vulgar
3. (slang) very good, awesome, crazy, sick, wild

   あの子 (こ)の制服 (せいふく)姿 (すがた)がヤバすぎる

   ano ko no seifuku-sugata ga yabasugiru

   she looks damn amazing in sailor uniforms

   (literally, “the sailor uniform appearance of that girl is too sick”)

やばい

1. oh no, crap

This is an example of a word that can be spelled with katakana to convey an informal conversational tone, as ヤバい.

• すごい (sugoi)
• まじ卍 (まんじ) (majimanji)

• Etymology at Gogen-Allguide (in Japanese)